> Aside, are the mega and giga prefixes ever used for anything except bits and bytes?

Sure, few examples of the top of my head:

- Megatons, as in yield of nuclear weapons. Which is a bit odd unit, should be in J, goddammit!

- Similarly, energy consumption/production. Commonly used units MWh, GWh, TWh. Again, the proper unit would be J, not Wh. Or Mtoe, for Million tons of oil equivalent.

> Megatons, as in yield of nuclear weapons. Which is a bit odd unit, should be in J, goddammit!

That’s what is odd about it? It should be teragrams.

It's a measure of energy, hence the unit should be J (with some appropriate prefix).

Peta- would be the appropriate prefix. 4.184 PJ is 1 megaton.

Yield of explosives is generally measured in kilograms of TNT, that's why.

Whoosh.

Actually, it should be grams. 51.3162(...) grams, to be somewhat precise.

It always feels a little grating when I hear someone say some number of "thousand kilometers".

Yes, describing my old car's odometer as "250 megameters" is oddly satisfying to let roll of the tongue.

I prefer to mix my references between metric & imperial: 1.55 deca-miles

Yes! Aside from the extremely common megahertz and gigahertz, commonly used units are megajoules, gigajoules, megawatts, gigawatts, terawatts, petajoules (when countries are negotiating about energy security), exajoules (when people measure world energy consumption), megohms, gigohms, megalitres (for the capacity of a dam, though teraliters would have been more appropriate), megapascals (of some kind of tensile strength typically), gigapascals (of Young's modulus typically), megaergs (back when people still used ergs), and so on.

Um yes, for ..., like EVERYTHING?

How much money do we have left in the budget -> Several k€.

Astronomical distances in kilo, mega and giga parsecs / light years.

Forces (e.g engine thrust) Kilo and Meganewtons.

output of powerplants are usually in the Megawatt to Gigawatt.

Frequencys of radio waves are Megahertz to Terahertz.

Energy of cosmic Ray's goes all the way up to zetta electronvolts.

I could name more

> and Megadeth.)

Laughed at that one.

Megadeth is named after the term “megadeath”, a unit in Cold War calculations of possible nuclear attacks to designate a million deaths. The 80’s were a grim time. (You can actually see in the film Dr. Strangelove a scene where George C. Scott’s character leans over a binder labeled “World Targets in Megadeaths”.)

Here in the Netherlands GJ (gigajoule) is used for buildings that use blockheating.

Mega-, giga- and terawatts are well used and relatively common. More specialised but still common enough are megaohms and mega/giga/terahertz.

Physicists studying the sun and effect on its surface use megameter as a length scale quite a bit.

Megahertz, Megawatt, Megapixel?

An engineering mechanics textbook that I used had megagram as a unit.

Gigawatts were popularized in a certain movie :)

Megatons of TNT equivalent for big bombs.

Are those metric tons or imperial tons? If metric, why aren't they gigakilograms (teragrams?) of TNT?

Answering my own question, "megatons of TNT" does refer to metric tons.